JP3265977B2 - Hot finish rolling method for hot rolled steel strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot finish rolling method for a hot rolled steel strip by a continuous hot finish rolling mill.

[0002]

2. Description of the Related Art Generally, a hot-rolled steel strip is formed by rolling a slab heated to a predetermined temperature to a predetermined thickness by a rough rolling mill to form a coarse bar, and then forming the coarse bar into a plurality of rolling stands. It is manufactured by finish rolling in a continuous hot finish rolling mill to form a hot-rolled steel strip having a predetermined thickness, and then cooling the hot-rolled steel strip on a run-out table and winding it up with a coiler.

[0003] In the finish rolling process of a hot-rolled steel strip by such a continuous hot finish rolling mill, waves are generated on both sides in the width direction of the hot-rolled steel strip to be finish-rolled, and waves are generated at the center. "Middle elongation" occurs, and "one-sided wave" occurs, in which a wave occurs only on one side.

[0004] When the above-mentioned deformation of the hot-rolled steel strip such as ear waves, medium elongation, and half-wave occurs, not only does the flatness of the steel strip decrease, but also the steel strip undergoing hot finish rolling is subjected to the rolling roll. Troubles such as "escape" to one side and "squeezing", which are folded, occur, so that stable finish rolling cannot be performed.

As means for solving the above-mentioned problems, conventionally, adjustment of the load distribution of the rolling load in each rolling stand of the continuous hot finishing mill, crossing of upper and lower rolling rolls, shift of shifting the center of the rolling roll, and roll bender are conventionally used. Adjustment of roll deflection and the like are performed, and the plate shape is adjusted by these adjustments.

[0006]

In recent years, as the hot rolled steel strip to be rolled becomes harder and thinner, hot finish rolling with a high load tends to be performed. When the load on the hot finish rolling is increased, the "waves" generated in the hot-rolled steel strip during the finish rolling become large, and when the thickness of the hot-rolled steel strip to be finish-rolled is small, the hot rolling during the finish rolling is performed. Since the centering of the steel strip is difficult to be performed, troubles such as "escape" and "drawing" are likely to occur.
Therefore, it is difficult to perform stable rolling by the above-described conventional method.

In general, in continuous hot rolling of a hot-rolled steel strip, if the tension between the rolling stands of the hot-rolled steel strip to be rolled is increased, the rolling load is reduced, and the flatness of the steel strip shape can be achieved by: Conceptually known. However, the optimal value of the tension that enables the finish rolling of a hot-rolled steel strip, particularly a thin material or a hard material, to be performed stably by a continuous hot finish rolling mill has not been elucidated yet, and the above-described problem still occurs.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and to produce deformations such as ear waves, middle elongation, and single waves when performing a finish rolling of a hot-rolled steel strip by a continuous hot finishing rolling mill. And a method for producing a hot-rolled steel strip with excellent flatness, in which hard and thin materials, particularly hard and thin materials, can be stably rolled in a good condition and a high-quality hot-rolled steel strip can be produced with high yield. To provide.

[0009]

SUMMARY OF THE INVENTION From the above-mentioned viewpoints, the inventors of the present invention have found that, when performing a finish rolling of a hot-rolled steel strip by using a continuous hot finishing rolling mill, the flatness of the hot rolled steel strip is excellent without deformation. As a result of intensive studies to develop a method of stably rolling a strip, the relationship between the tension between each stand of the hot-rolled strip to be finish-rolled, the rolling load, and the flatness of the strip. In the above, the rolling tension between the stands having excellent flatness and obtaining a good rolling state was found.

[0010] The present invention is characterized in that the slab heated to a predetermined temperature is roughly rolled by a rough rolling mill, and then subjected to finish rolling to a hot-rolled steel strip by a continuous hot finishing rolling mill comprising a plurality of rolling stands. against hot rolled strip to be rolled in a continuous hot finish rolling mill, and it has the characteristics to be in the range tension of 5 kgf / mm ² exceeding ~10kgf / mm ² to load between the rolling stands.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is necessary that the tension applied between each stand to a hot-rolled steel strip rolled by a continuous hot finish rolling mill should exceed 5 kgf / mm ² . By applying a tension exceeding 5 kgf / mm ^{2 in} this way, excellent flatness can be imparted to the steel strip to be rolled.

The tension applied between the stands is 5 kgf /
If it is less than ² mm , deformation such as ear waves, middle elongation, and half wave generated in the hot-rolled steel strip cannot be prevented, and the flatness of the steel strip decreases. On the other hand, if the tension applied between the stands is 10
If the value exceeds kgf / mm ² , the tensile stress of the steel strip is reduced, so that the steel strip is broken, and restrictions are imposed on equipment.

Therefore, in the present invention, the tension applied between the stands to the hot-rolled steel strip rolled by the continuous hot finish rolling mill exceeds 5 kgf / mm ^{2 to} 10 kgf / m ^2.
It should be limited to a range of m ^2. By setting the tension at the time of hot finish rolling within the above-mentioned range, deformation such as ear waves, middle elongation, and half wave does not occur in the hot-rolled steel strip, the flatness thereof is increased, and particularly, the hard material is hardened. In addition, the hot-rolled steel strip of a thin material can be finish-rolled stably. Furthermore, as a result of reducing the rolling load on the steel strip at each rolling stand, damage to the rolling rolls is reduced, and the number of continuous rolling operations can be extended.

[0014]

Next, the method of the present invention will be further described with reference to examples. C: 0.13 wt.%, Si: 0.02 wt.%, M
n: a slab containing 0.8 wt.% as a main component is roughly rolled by a roughing mill, and then, a continuous hot-finishing rolling mill consisting of 7 stands is used. Finish rolling was performed under a rolling load to prepare specimens (hereinafter, referred to as specimens of the present invention) Nos. 4 and 5 of hot-rolled steel strips having a thickness of 1.6 mm and a width of 1200 mm , and reference specimens 1 to 3 . .

For comparison, a slab having the same composition as above is roughly rolled, and then finish-rolled with a tension and a predetermined rolling load outside the range of the present invention. Specimens (hereinafter referred to as comparative specimens) Nos. 1 to 4 of hot-rolled steel strips having different widths were prepared.

[0016]

[Table 1] The present invention specimen No. 4, 5, referential specimen No. The flatness of Nos. 1 to 3 and Comparative Sample Nos. 1 to 4 were examined, and the rolled state is shown in Table 1 together. The flatness is shown in FIG.
As shown in the above, the wavelength and the wave height of the wave generated in the steel strip were expressed by flatness = wave height / wavelength × 100 (%).

As is apparent from Table 1, the tension applied to the hot-rolled steel strip between the rolling stands was 0.50 Kgf / mm ² and 1.00 Kgf / mm ^2, which was out of the range of the present invention and was small for comparison. Specimens No. 1 and 2 have a flatness of 5.0%
And 2.5% was bad, and the rolling situation was poor.
In addition, the comparative specimen No. 3 in which the tension applied to the hot-rolled steel strip was 12.00 Kgf / mm ² , which was larger than the scope of the present invention, was broken during rolling, and was applied to the hot-rolled steel strip. Tension 15.00 Kg
Comparative specimen No. 4 having an f / mm ² was unable to be rolled due to equipment limitations.

On the other hand, the specimens Nos. 4 and 5 of the present invention in which the tension applied to the hot-rolled steel strip is within the scope of the present invention ,
Specimens 1 to 3 had a flatness of 1.0% or less, a good rolling state, and a reduced rolling load as compared with comparative specimens Nos. 1 and 2.

[0019]

As described above, according to the method of the present invention, when finishing rolling of a hot-rolled steel strip by a continuous hot finishing rolling mill, deformations such as ear waves, middle elongation, and single waves occur. Without
Hot-rolled steel strips with high flatness, especially hard materials and thin materials, can be rolled stably in good condition, and the industrially useful effect of producing high-quality hot-rolled steel strips with high yield is brought about. It is.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for calculating flatness of a steel sheet.

Continued on the front page (72) Inventor Hiroshi Sekine 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Shozo Higashi 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Hayato Murata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-60-44106 (JP, A) JP-A-9-225504 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21B 1/00-1/46 B21B 37/00-37/78

Claims (1)

(57) [Claims] 1. A slab heated to a predetermined temperature is roughly rolled by a rough rolling mill, and then subjected to finish rolling to a hot-rolled steel strip by a continuous hot finishing rolling mill comprising a plurality of rolling stands. The tension applied between the rolling stands to the hot-rolled steel strip rolled by the finishing mill is 5 kgf /
characterized in that in the range of mm ² exceeding ~10kgf / mm ^2, the hot finish rolling process of hot rolled strip.